Ionic liquid alkylation of isobutane with ethylene to produce alkylate

ABSTRACT

A process for producing high octane alkylate is provided. The process involves reacting isobutane and ethylene using an ionic liquid catalyst. Reaction conditions can be chosen to assist in attaining, or to optimize, desirable alkylate yields and/or properties.

CROSS-REFERENCE OF RELATED APPLICATIONS

This application claims the priority benefit of U.S. Provisional PatentApplication No. 63/289,685, filed Dec. 15, 2021, the disclosure of whichis incorporated herein by reference.

FIELD

This present disclosure relates a process for isoparaffin-olefinalkylation. More specifically, the present disclosure relates to aprocess for producing a high octane alkylate by reacting isobutane withethylene in the presence of an acidic ionic liquid catalyst.

BACKGROUND

Because of its clean-fuel properties (e.g., high octane rating,low-vapor pressure, and low sulfur content), alkylate is considered oneof the most desired components in the gasoline pool. As demand forcleaner-burning fuel has increased, refiners are relying more than everon alkylate to meet stringent gasoline specifications. With increasingpressure to reduce motor vehicle exhaust emissions, alkylate iswell-positioned to be in steady demand for decades to come.

Most alkylate is produced in refineries by a process known asisoparaffin alkylation. Commercially, isoparaffin alkylation is an acidcatalyzed reaction that combines C3-C5 light olefins from a fluidcatalytic cracking (FCC) unit with isobutane to produce a relativelyhigh octane branched-chain paraffinic hydrocarbon fuel, includingiso-heptane and iso-octane. Predominant alkylation technologies utilizedby refiners require a liquid acid catalyst such as sulfuric acid (H₂SO₄)or hydrofluoric acid (HF).

Ethylene is another major component produced in the FCC unit. However,the direct alkylation of ethylene has not been possible withconventional liquid acid alkylation catalysts (e.g., H₂SO₄, HF) andprocesses due to the relatively slow kinetics of the reaction. Effortsto produce alkylate from ethylene have relied on dimerizing ethylene tobutylene in a dimerization process unit, followed by alkylation withisobutane in the alkylation process unit. This method requiressignificant extra capital investment for the dimerization unit. Inaddition, alkylate yield per barrel of ethylene is very low.

Therefore, there is a need for an improved process for alkylation oflight olefins.

SUMMARY

In one aspect, there is provided an alkylation process comprising:passing an isobutane feed and an ethylene feed to an alkylation reactor,wherein the alkylation reactor contains an ionic liquid catalyst, theionic liquid catalyst comprising an organic cation and a halometallateanion, for reacting the isobutane and ethylene to generate an alkylatehaving a research octane number (RON) of 93 or more; wherein thealkylation reactor is operated at reaction conditions including atemperature of from 30° C. to 100° C., a pressure of from 300 psig to700 psig (2068 kPa to 4826 kPa), an overall paraffin to olefin molarratio from 2 to 20, and a residence time of from 5 minutes to 1 hour.

In another aspect, there is provided an alkylate having a researchoctane number (RON) of 93 or more, comprising: (i) at least 70 wt. % C6paraffins, wherein the C6 paraffins comprise isomers of dimethylbutane(DMB) and methylpentane (MP) and a molar ratio of DMB to MP is at least7:1; (ii) 30 wt. % or less C8 paraffins; and (iii) less than 20 wt. %C9+ paraffins.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of one embodiment of an alkylation process ofthe present disclosure.

FIG. 2 is an illustration of one embodiment of an alkylation process ofthe present disclosure.

DETAILED DESCRIPTION Definitions

The term “alkylate” means the reaction products generated in alkylationreactions between an olefin and an isoparaffin in the presence of acatalyst. Alkylates typically are highly branched paraffinichydrocarbons. Refiners can use alkylate as a gasoline blend stock toboost octane, reduce Reid vapor pressure (RVP), and reduce olefincontent in a final gasoline blend.

The term “Cn hydrocarbons” or “Cn”, wherein “n” is a positive integer,means hydrocarbons having “n” number of carbon atoms. The term “Cn+” ismeant to describe a mixture of hydrocarbons having “n” or more carbonatoms. The term “Cn−” is meant to describe to a mixture of hydrocarbonshaving “n” or less carbon atoms.

The term “octane number” refers to the percentage of iso-octane in amixture of iso-octane and n-heptane that would have the same knockresistance as the presently tested fuel, according to ASTM D2699 andD2700. Octane numbers typically range from 0 to 100, with higher valuesindicating better fuel performance. Octane numbers are unitless.

The term “Research Octane Number” (RON) refers to the octane numberobtained by testing at lower engine speed and temperature, typicallyabout 600 rpm, according to ASTM D2699.

The term “Motor Octane Number” (MON) refers to the octane numberobtained by testing at higher engine speed and temperature, typicallyabout 900 rpm according to ASTM D2700. Given that engine inefficiencyinherently increases as temperature increases, RON is typically higherthan MON.

“Anti-knock index” is defined by the arithmetic average of the twooctane numbers: (RON+MON)/2.

The terms “wt. %”, “vol. %”, or “mol. %” refers to a weight, volume, ormolar percentage of a component, respectively, based on the totalweight, the total volume of material, or total moles, that includes thecomponent. In a non-limiting example, 10 grams of component in 100 gramsof the material is 10 wt. % of component.

Isobutane Feed

The isobutane feed stream to alkylation unit generally comprises atleast 50 wt. % isobutane (e.g., 50 wt. % to 99 wt. % isobutane, or 50wt. % to 95 wt. % isobutane, or 55 wt. % to 90 wt. % isobutane, or atleast 80 wt. % isobutane, or 80 wt. % to 98 wt. % isobutane, or 90 wt. %to 97 wt. % isobutane), with at least 90 wt. % (e.g., at least 99 wt. %)of the remainder comprising n-butane. The isobutane feed may besubstantially free of one or more of (i) butenes, including isobutene,(ii) C5+ hydrocarbon, and (iii) C3-hydrocarbon. In this context, theterm “substantially free” means the isobutane feed comprises less thanor equal to 1.0 wt. % of the designated compounds (e.g., less than orequal to 0.1 wt. %, or less than or equal to 0.01 wt. %, or less than orequal to 0.001 wt. %).

Ethylene Feed Stream

Ethylene feed streams useful herein may include dilute ethylene streams,containing up to 50 wt. % ethylene, for example. In some aspects, theethylene feed stream may include a low purity ethylene feed, including60 wt. % to 95 wt. % ethylene. In other aspects, the ethylene feedstream may include high purity ethylene (95 wt. % to 99+ wt. %ethylene).

The dilute ethylene stream derived from any number of refinery streams.The dilute ethylene stream may be an off-gas from a refinery unitselected from an ethylene cracker, a fluid catalytic cracker, a coker, anaphtha cracker, a Fischer-Tropsch synthesis unit, an ethylenepolymerization unit, or a pyrolysis unit.

The dilute ethylene stream may contain from 0.1 wt. % to 50 wt. %ethylene, such as from 5 wt. %, 10 wt. %, or 15 wt. % to 30 wt. %, 40wt. %, or 50 wt. % ethylene. A suitable dilute ethylene stream maycomprise from 5 wt. % to 50 wt. % ethylene. The balance of the diluteethylene stream may include hydrogen, nitrogen, methane, ethane,propylene, and/or propane. For example, a typical FCC off-gas mayinclude 50 wt. % to 70 wt. % methane and hydrogen, with the balancebeing about equal parts ethane and ethylene, as well as a minor amountof C3+ compounds.

In some aspects, the ethylene feed stream may be a polymer-gradeethylene stream, which may have at least 98 wt. %, or at least 99 wt. %,or at least 99.5 wt. %, or at least 99.8 wt. % ethylene.

Ionic Liquid

The ionic liquid comprises an organic cation and an anion. The organiccation is generally a nitrogen-based cation, a phosphorus-based cation,or a combination thereof. Representative organic cations includeammonium, pyrrolidinium, pyridinium, imidazolium, and phosphoniumcations.

Examples of ammonium cations include tetraalkylammonium cations, such astri(C1-C6 alkyl)-(C2-C10 alkyl)ammonium cations. Representative ammoniumcations include trimethyl-n-propylammonium, n-butyl-trimethylammonium,n-hexyl-trimethylammonium, triethyl-methylammonium, tetraethylammonium,n-butyl-triethylammonium, and tetra-n-butylammonium.

Examples of pyrrolidinium cations include N-alkylpyrrolidinium cations,such as N—(C2-C6 alkyl)pyrrolidinium cations, andN,N-dialkylpyrrolidinium cations, such as N—(C1-C3 alkyl)-N—(C2-C6alkyl)pyrrolidinium cations. Representative pyrrolidinium cationsinclude N-propylpyrrolidinium, N-butylpyrrolidinium,N-methyl-N-propylpyrrolidinium and N-butyl-N-methylpyrrolidinium.

Examples of imidazolium cations include 1,3-dialkylimidazolium cations,such as 1-(C2-C10 alkyl)-3-(C1-C3 alkyl)imidazolium cations.Representative imidazolium cations include 1-ethyl-3-methylimidazolium,1-n-butyl-3-methylimidazolium, 1-n-hexyl-3-methylimidazolium, and1-n-octyl-3-methylimidazolium.

Examples of pyridinium cations include N-alkylpyridinium cations, suchas N—(C2-C6 alkyl)pyridinium cations, and N-alkyl-alkylpyridiniumcations, such as N—(C2-C6 alkyl)-(C1-C3 alkyl)pyridinium cations.Representative pyridinium cations include N-ethylpyridinium,N-butylpyridinium, N-propyl-4-methylpyridinium andN-butyl-4-methylpyridinium.

Examples of phosphonium cations include tetraalkylphosphonium cations,such as tri(C1-C10 alkyl)-(C2-C20 alkyl)phosphonium cations.Representative phosphonium cations include triethyl-pentylphosphonium,tetrabutylphosphonium, and trihexyl-tetradecylphosphonium.

The anion of the ionic liquid comprises a halometallate. Halometallateanions may contain a metal selected from Al, Ga, In, Mn, Fe, Co, Ni, Cu,Zn, or combinations thereof, and a halide selected from F, Cl, Br, I, orcombinations thereof. In some aspects, the anion of the ionic liquidcomprises a haloaluminate. In some aspects, the anion of the ionicliquid comprises a chloroaluminate. For catalytic applications requiringLewis acidity (such as alkylation), the ratio of moles of halide tomoles of metal in the halometallate anion is less than 4. The anion maybe formally an anion or it may be an anion associated with a metalhalide. For instance, the anion may be AlCl₄ ⁻ or Al₂Cl₇ ⁻ associatedwith AlCl₃. In some aspects, the anion may be GaCl₄ ⁻ or Ga₂Cl₇ ⁻ orGa₃Cl₁₀ ⁻ associated with GaCl₃

The ionic liquid catalyst can include a co-catalyst (or catalystpromoter) to enhance the activity of the ionic liquid catalyst byboosting its overall acidity. The co-catalyst may be a Brønsted acidand/or a Brønsted acid precursor. The co-catalyst is present in anamount of 0.05 mol to 1 mol of co-catalyst per mol of ionic liquid, or0.05 mol to 0.7 mol, or 0.05 mol to 0.5 mol, or 0.1 mol to 0.7 mol, or0.1 mol to 0.5 mol. Suitable Brønsted acids include HCl, HBr, HI, andcombinations thereof. In some aspects, the co-catalyst can be generatedin situ from appropriate Brønsted acid precursors. Suitable Brønstedacid precursors include chloroalkanes such as 1-chloropropane,2-chloropropane, 1-chlorobutane, 2-chlorobutane,1-chloro-2-methylpropane, 2-chloro-2-methylpropane, and otherchloroalkanes, preferably secondary or tertiary chloroalkanes, orcombinations thereof. In some aspects, the Brønsted acid precursor is achloroalkane having more than one chloride atom per molecule such asdichloromethane, chloroform, carbon tetrachloride, tetrachloroethylene,tetrachloropropene, or combinations thereof.

Alkylation

Typical alkylation reaction conditions include a minimum temperature of30° C., or 35° C., or 40° C., or 45° C., or 50° C., or 55° C., or 60°C.; additionally or alternatively, a maximum temperature of 100° C., or95° C., or 90° C., or 85° C., or 80° C., or 75° C., or 70° C. Generally,the temperature can be in a range from any minimum temperature disclosedherein to any maximum temperature disclosed herein. It is preferred tohave the ionic liquid that maintains its liquid state through theoperating temperature range.

The alkylation reaction can be conducted at a pressure of from 100 psigto 1000 psig (689 kPa to 6895 kPa), such as 300 psig to 700 psig (2068kPa to 4826 kPa), or 350 psig to 500 psig (2413 kPa to 3447 kPa).Preferably, the reactants are maintained in a liquid state at theoperating pressure.

The residence time of the reactants in the reaction zone is in a rangeof from a few seconds to several hours (e.g., 30 seconds to 1 hour, or 2minutes to 30 minutes, or 2 minutes to 10 minutes, or 5 minutes to 1hour, or 5 minutes to 30 minutes, 5 minutes to 10 minutes).

The volume of ionic liquid in the reactor may be in a range of from 1vol. % to 75 vol. % of the total volume of material in the reactor(ionic liquid and hydrocarbons), or 1 vol. % to 70 vol. %, or 1 vol. %to 65 vol. %, or 1 vol. % to 60 vol. %, or 1 vol. % to 55 vol. %, or 1vol. % to 50 vol. %, or 1 vol. % to 45 vol. %, or 1 vol. % to 40 vol. %,or 1 vol. % to 35 vol. %, or 1 vol. % to 30 vol. %, or 1 vol. % to 25vol. %, or 1 vol. % to 20 vol. %, or 1 vol. % to 15 vol. %, or 1 vol. %to 10 vol. %, or 1 vol. % to 5 vol. %. In aspects where the volume ofionic liquid in the reactor is less than 50 vol. %, the reaction mixturecomprises a dispersed ionic liquid phase and a continuous hydrocarbonphase. In aspects where the volume of ionic liquid in the reactor isgreater than 50 vol. %, the reaction mixture comprises a dispersedhydrocarbon phase and a continuous ionic liquid phase.

Due to the low solubility of hydrocarbons in ionic liquids,isoparaffin-olefin alkylation, like most reactions in ionic liquids, isgenerally biphasic. The catalytic alkylation reaction is generallycarried out in a mixed phase liquid-liquid system. The system can be abatch system, a semi-batch system, or a continuous system as is usualfor aliphatic alkylation. Vigorous mixing is desirable to ensure goodcontact between the reactants and the catalyst.

The isoparaffin and olefin can be introduced in the reactor separatelyor as a mixture, in one or multiple locations. The molar ratio ofisoparaffin to olefin is generally 20:1 or less, or 15:1 or less, or10:1 or less, or in a range of 2:1 to 20:1, or in a range of 2:1 to15:1, or in a range of 2:1 to 10:1, or in a range of 2:1 to 8:1, or in arange of 2:1 to 6:1, or in a range of 2:1 to 4:1, or in a range of 5:1to 20:1, or in a range of 5:1 to 15:1, or in a range of 5:1 to 10:1.

In a semi-batch system, the catalyst, optional co-catalyst, and at leasta portion of the isoparaffin are introduced with no olefin present,followed by the olefin or a mixture of isoparaffin and olefin. In asemi-batch system, the olefin is added gradually over a period of time.The catalyst is measured in the reactor with respect to the amount oftotal olefins added over the course of the reaction, with a catalyst toolefin weight ratio in a range of from 0.1:1 to 10:1 (e.g., 0.2:1 to5:1, or 0.5:1 to 2.5:1).

In a continuous system, the ionic liquid catalyst, the isoparaffin, theolefin, and optionally the co-catalyst are each added continuously.Catalyst, optional co-catalyst, unreacted isoparaffin, and unreactedolefin are each removed continuously from the reaction zone along withalkylate product. The catalyst, co-catalyst, unreacted isoparaffin,and/or unreacted olefin may be recycled. The olefin may be added to oneor more locations in the reaction zone. It is preferable to add theolefin to multiple locations in the reaction zone. Adding olefin inmultiple locations or spreading the olefin addition over a longer periodof time, results in the isoparaffin to olefin ratio measured in aspecific location at a specific point in time to be higher. Theisoparaffin to olefin ratio is defined as the cumulative amount ofisoparaffin divided by the cumulative amount of olefin added across theentire reaction zone.

Heat generated by the alkylation reaction can be removed using any ofthe methods known to those of skill in the art.

Conjunct polymer forms as a by-product of the alkylation reaction.Conjunct polymers are typically highly conjugated, olefinic, highlycyclic hydrocarbons and have a strong affinity for the ionic liquidcatalyst. The ionic liquid catalyst loses its effectiveness over time asthe amount of conjunct polymer increases. Over time, the ionic liquidcatalyst must then either be replaced or regenerated. Generally, only asmuch ionic liquid catalyst is regenerated as is necessary to maintain adesired level of catalyst activity. Generally, the alkylation process isoperated at conditions sufficient to maintain a desired level ofconjunct polymer in the ionic liquid. The amount of conjunct polymer inthe ionic liquid during alkylation may be maintained at 10 wt. % or less(e.g., 9 wt. % or less, or 8 wt. % or less, or 7 wt. % or less, or 6 wt.% or less, or 5 wt. % or less, or 4 wt. % or less, or 3 wt. % or less,or 2 wt. % or less, 1 wt. % or less). For example, the amount ofconjunct polymer in the spent ionic liquid may be maintained in a rangeof from 0.5 to 10 wt. %, or 1 to 5 wt. %, or 2 to 4 wt. %. An amount ofconjunct polymer in an ionic liquid phase can be measured using infraredspectroscopy, such as disclosed in U.S. Pat. No. 9,290,702.

At the reactor outlet, the hydrocarbon phase is separated from the ionicliquid phase by gravity settling based on density differences, or byother separation techniques known to those skilled in the art. Then thehydrocarbons are separated by distillation, and the starting isoparaffinwhich has not been converted is recycled to the reactor. The catalyst istypically recycled to the reactor as well.

Typical alkylation conditions may include a temperature of from 30° C.to 100° C., a pressure of from 300 psig to 700 psig (2068 kPa to 4826kPa), an isoparaffin to olefin molar ratio of from 2:1 to 20:1, aresidence time of from 5 minutes to 1 hour, an ionic liquid volume inthe reactor of from 1 vol % to 70 vol %.

The conversion of ethylene is typically at least 95% (e.g., at least96%, or at least 97%, or at least 98%, or at least 99%). The percentethylene conversion is defined as: (the amount of ethylene added to thereactor minus the amount of ethylene remaining after the reaction (or atthe reactor outlet)) divided by the total amount of ethylene added tothe reactor times 100. In a continuous process, ethylene conversion isdefined as: (the amount of ethylene added to the reactor minus the totalflow of ethylene out of the reactor) divided by the total flow ofethylene into the reactor.

FIG. 1 illustrates one embodiment of an alkylation process according tothe present disclosure. An isobutane feed stream 105, an ethylene feedstream 110, and an ionic liquid catalyst composition stream 115,optional co-catalyst, are fed to an alkylation zone 120. The isobutaneand the ethylene react in the presence of the ionic liquid catalystcomposition to form alkylate.

The effluent 125 from the alkylation zone 120 contains alkylate,unreacted isobutane, the ionic liquid catalyst, and possibly unreactedethylene. The effluent 125 is sent to a separation zone 130 where it isseparated into a hydrocarbon stream 135 comprising the alkylate andunreacted isobutane (and any unreacted ethylene) and an ionic liquidrecycle stream 140. Suitable separation zones include gravity settlers,coalescers, filtration zones comprising sand or carbon, adsorptionzones, scrubbing zones, or combinations thereof.

The hydrocarbon stream 135 is sent to a hydrocarbon separation zone 145where it is separated into an alkylate stream 150 and an isobutane andco-catalyst recycle stream 155. The alkylate stream 150 can be recoveredand further treated as needed. The isobutane and co-catalyst recyclestream 155 can be recycled to the alkylation zone 120, if desired.Suitable hydrocarbon separation zones include distillation orvaporization.

The ionic liquid recycle stream 140 which typically contains some amountof conjunct polymer is also recovered from the separation zone 130 andcan be recycled to the alkylation zone 120, if desired. In someembodiments, at least a portion 160 of the ionic liquid recycle stream140 can be sent to a regeneration zone 165 to remove at least some ofthe conjunct polymer from the ionic liquid recycle stream to provide aregenerated ionic liquid. The regenerated ionic liquid recycle stream170 can be recycled to the alkylation zone 120.

Alkylate

In some aspects, the process can be used to upgrade low value C4hydrocarbons to higher value alkylates. To that extent, one specificaspect is the alkylation of isobutane with ethylene to generate C6compounds. Preferred products include isomers of dimethylbutane (DMB),namely, 2,3-dimethylbutane and 2,2-dimethylbutane. Other C6 isomers arealso produced. One set competing isomers are methylpentanes (MP), namely2-methylpentane and 3-methylpentane. The quality of the alkylate can bemeasured in the ratio of DMB to MP, with a high ratio desired (e.g., atleast 7:1 or more, or at least 10:1 or more, or at least 12:1 or more,or at least 15:1 or more, or at least 20:1 or more).

In some aspects, the alkylation reaction can have a selectivity for C6of at least 65% or more, or at least 70% or more, or at least 75% ormore. Selectivity for C6 is defined here as the total weight of productscontaining exactly six carbon atoms divided by the total weight ofproducts containing five or more carbon atoms. In some aspects, thealkylate can have a mole ratio of dimethylbutane to methylpentane of atleast 4:1 or more, or 7:1 or more, or at least 10:1 or more, or at least12:1 or more, or at least 15:1 or more, or 20:1 or more, or 25:1 ormore, or 30:1 or more, or 35:1 or more.

The alkylate may contain C8 paraffins. Preferred products includeisomers of trimethylpentane (TMP), namely 2,2,3-trimethylpentane,2,2,4-trimethylpentane, 2,3,3-trimethylpentane, and2,3,4-trimethylpentane. Other C8 isomers are also produced. One set ofcompeting isomers are dimethylhexanes (DMH), namely 2,2-dimethylhexane,2,3-dimethylhexane, 2,4-dimethylhexane, 2,5-dimethylhexane,3,3-dimethylhexane, and 3,4-dimethylhexane. The quality of the productstream can be measured in the ratio of total TMP to total DMH, with ahigher ratio desired (e.g., of greater than 2:1, or greater than 3:1).C8 isomers may be present in an amount of 30 wt. % or less (e.g., 1 wt.% to 30 wt. %, or 5 wt. % to 15 wt. %) of the alkylate.

The alkylate may contain C9+ paraffins. The C9+ paraffins may be presentin an amount of less than 20 wt. % (e.g., less than 10 wt. %) of thealkylate.

In some embodiments, the alkylate has a research octane number (RON) of93 or more (e.g., 94 or more, 95 or more, 96 or more, 97 or more, 98 ormore, 99, or 100 or more).

EXAMPLES

The following illustrative examples are intended to be non-limiting.

Example 1 Ionic Liquid Catalyst

The ionic liquid catalyst used herein was N-butylpyridiniumchloroaluminate, which was prepared according to U.S. Pat. No.7,495,144. Table 1 shows the chemical composition of the catalyst.

TABLE 1 Composition of the N-Butylpyridinium Chloroaluminate IonicLiquid Catalyst Element Weight % Al 12.4 Cl 56.5 C 24.6 H 3.2 N 3.3

Examples 2-5 Alkylation of Isobutane with Ethylene UsingN-Butylpyridinium Chloroaluminate Ionic Liquid Catalyst

To a 100-1000 mL Parr autoclave reactor, isoparaffin feed controlled bya Quizix pump, olefin controlled by a Bronkhorst flow controller, HClco-catalyst controlled by a Bronkhorst flow controller, and ionic liquidcatalyst controlled by a LEWA pump were continuously fed. Both thehydrocarbon feed and HCl co-catalyst were fed to the top of the reactorwhile the ionic liquid was fed to the bottom of the reactor. The reactorcontents were heated to a target temperature under a target pressurewith overhead stirring. The target process conditions are shown inExamples. The reactor effluent was taken from the top of the reactor.The reactor effluent was separated in a downstream separator into aseparate product phase and an ionic liquid catalyst phase. The productwas analyzed by gas chromatography.

Isobutane was obtained from a refinery FCC stream. The ethylene feed wasUltra-High Purity (UHP) grade ethylene purchased from Airgas. Table 2shows the chemical composition of the isobutane and ethylene feeds. FIG.2 shows a simplified process flow diagram for alkylation of isobutanewith ethylene.

TABLE 2 Composition of the Isobutane and Ethylene Feeds Isobutane FeedWeight % Propane 6.3 Isobutane 79.9 n-Butane 12.4 Isopentane 1.4Ethylene Feed Ethylene 99.9

Table 3 shows conditions and results for isobutane alkylation withethylene.

TABLE 3 Conditions and Results for Isobutane Alkylation with EthyleneEx. 2 Ex. 3 Ex. 4 Ex. 5 Alkylation Conditions Temperature [° F.] 140 120100 90 Pressure [psig] 400 400 400 180 Isoparaffin/Olefin molar ratio 88 8 8 Ionic Liquid Content [vol. %] 10 10 10 10 Residence Time [min] 8 810 6 Olefin/HCl molar ratio 30 30 25 47 Ethylene Conversion [%] 98.096.0 99.7 38.0 Alkylate Properties Cn Selectivity [%] C5 0.9 2.9 7.0 2.4C6 87.2 85.1 71.4 55.9 C7 1.1 1.4 4.2 3.0 C8 8.1 6.9 10.0 26.3 C9 0.30.8 2.1 3.0 C10 1.0 1.3 2.6 4.7 C11 0.7 0.6 1.7 3.5 C12+ 0.8 1.0 1.0 1.2C6 Isomer Relative Distribution [%] 2,2-Dimethylbutane 0 1 2 0.32,3-Dimethylbutane 97 96 78 97 2-Methylpentane 2 3 12 2.83-Methylpentane 1 1 5 0 Dimethylbutane/Methylpentane 32.3 24.3 4.7 34.8molar ratio C8 Isomer Relative Distribution [%] Trimethylpentanes 70 6853 47 Dimethylhexanes 21 19 34 50 Methylheptanes 8 11 12 3 Octane NumberRON 101.0 100.4 94.3 96.8 MON 93.8 93.4 90.4 91.0 SIMDIST (ASTM D2887)[° F.] T50 136 138 137 157 T90 192 193 227 285 T99 295 293 378 418 FBP(T99.5) 356 363 423 441

The results show that alkylate produced from direct conversion ofisobutane with ethylene by highly active ionic liquid catalyst containedpredominantly C6 and C8 paraffins. Product selectivity to C6 alkylate(reaction product of 1 mole of ethylene and 1 mole of isobutane) and C8alkylate (reaction product of 2 mole of ethylene and 1 mole ofisobutane) can be controlled. Different amounts of C6 and C8 can beproduced depending on process conditions selected.

The C8 isomer distribution can vary depending upon the conditionsselected. C8 isomers can be predominately high-octane numbertrimethylpentanes or predominately low-octane number dimethylhexanes. Atrelatively lower reaction temperatures and lower reaction pressure, theoverall C6 selectivity significantly decreased and C8 selectivitysignificantly increased. Among C8 isomers, low-octane numberdimethylhexanes significantly increased while high-octanetrimethylpentanes significantly decreased, resulting in a poor qualityalkylate.

Under carefully selected and controlled process conditions (Examples2-4), high conversion of ethylene was achieved (>96%). When the reactiontemperature and pressure were not sufficiently high, however, theconversion of ethylene was very low at 38%, and a substantial amount ofethylene was found unreacted (Example 5). These results were surprisingcompared with the conventional C3 and C4 olefin alkylation processeswhere nearly 100% conversion of olefins is observed with an ionic liquidcatalyst. This indicates that ethylene has very low reactivity comparedwith C3 and C4 olefins.

As the reactor temperature was lowered from 140° F. to 100° F. (Examples2-4), a decline in the RON octane number from 101 to 94 was observed.These results were surprising in comparison to conventional C3 and C4olefin alkylation processes where lower temperatures provide alkylatewith better RON octane numbers. Furthermore, it was surprising todiscover that the C8 isomer distribution, as a function of temperature,for ethylene alkylation was the opposite of what is observed forconventional C3 and C4 olefin alkylation. At lower reactiontemperatures, dimethylhexanes significantly increased whiletrimethylpentanes significantly decreased, resulting in poorer alkylatequality (lower octanes) for ethylene alkylation. For C3 and C4 olefinalkylation, lower reaction temperatures increased trimethylpentanessignificantly, the opposite trend (see Examples 8-9).

Example 6 (Comparative) Alkylation of Isopentane with Ethylene UsingN-Butylpyridinium Chloroaluminate Ionic Liquid Catalyst

Alkylation of isopentane with ethylene using N-butylpyridiniumchloroaluminate ionic liquid catalyst was carried in accordance withU.S. Pat. No. 7,432,408.

Conditions and results for isopentane alkylation with ethylene are shownin Table 5 below.

Example 7 (Comparative) Alkylation of Isobutane with C3/C4 Olefins UsingN-Butylpyridinium Chloroaluminate Ionic Liquid Catalyst

For Examples 7-9, refinery isobutane containing 85% isobutane and 15%n-butane was used after drying with 13× molecular sieve.

A refinery olefin stream containing a mixture of C3 and C4 olefins(C3/C4 olefins) was dried with 13× molecular sieve and isomerized with aPd/Al₂O₃ catalyst at 150° F., 250 psig in the presence of hydrogen toproduce an isomerized C3/C4 olefin feed with the composition shown inTable 4.

TABLE 4 Composition of C3/C4 Olefin Feed Component Mol. % Propane 13.3Propylene 25.4 1-Butene 2.3 2-Butene 16.2 Isobutylene 6.7 n-Butane 12.4Isobutane 22.2 C5+ 1.6

Evaluation of C3/C4 olefin alkylation with isobutane was performed in acontinuously stirred tank reactor. An 8:1 molar mixture of isobutane andolefin was fed to the reactor with vigorous stirring. Ionic liquidcatalyst (N-butylpyridinium chloroaluminate) was fed to the reactor viaa second inlet port targeting to occupy 6 vol. % in the reactor. A smallamount of n-butyl chloride was added to produce anhydrous HCl gas. Theaverage residence time (combined volume of feeds and catalyst) was about12 minutes. The outlet pressure was maintained at 200 psig and thereactor temperature was maintained at 95° F. (35° C.) using externalcooling.

The reactor effluent was separated with a coalescing separator into ahydrocarbon phase and an ionic liquid catalyst phase. The hydrocarbonstream was further separated into multiple streams with threedistillation columns: a gas stream containing C3− hydrocarbons, an n-C4stream, an i-C4 stream and an alkylate stream. The ionic liquid catalystwas recycled back to the alkylation reactor for repeated use. Tomaintain the activity of the ionic liquid catalyst, a fraction of usedionic liquid catalyst was sent to a hydrogenation reactor for areduction of the amount of conjunct polymer in the ionic liquidcatalyst. The amount of conjunct polymer in the ionic liquid catalystwas maintained in a range of from 2-6% to obtain good quality alkylategasoline. The amount of conjunct polymer in the ionic liquid catalystwas determined by Fourier transform infrared (FT-IR) spectroscopy inaccordance with U.S. Pat. No. 9,290,702.

Table 5 shows conditions and results for isobutane alkylation with C3/C4olefins.

Examples 8-9 (Comparative) Alkylation of Isobutane with C4 Olefins UsingN-Butylpyridinium Chloroaluminate Ionic Liquid Catalyst

Alkylation was carried out as described in Examples 2-5 except that theolefin was a mixture of C4 olefins.

Table 5 shows conditions and results for isobutane alkylation with C4olefins.

TABLE 5 Conditions and Results for Isoparaffin-Olefin Alkylation Ex. 2Ex. 6 Ex. 7 Ex. 8 Ex. 9 Olefin Feed C2 C2 C3/C4 C4 C4 Isoparaffin Feedi-C4 i-C5 i-C4 i-C4 i-C4 Alkylation Conditions Temperature [° F.] 140122 95 95 50 Pressure [psig] 400 300 200 150 150 Isoparaffin/Olefin moleratio 8 4 8 8 8 Ionic Liquid Content [vol. %] 10 15 6 4 5 Residence Time[min] 8 40 12 4 5 Olefin/HCl mole ratio 30 — 60 49 40 Olefin Conversion[%] 98.0 95.0 100 100 100 Alkylate Properties Cn Selectivity [%] C5 0.94.1^((a)) 4.5 6.0 C6 87.2 8.0 6.3 6.9 C7 1.1 63.3 7.0 5.2 C8 8.1 9.166.4 65.0 C9 0.3 7.1 9.2 8.3 C10 1.0 4.2 3.1 4.6 C11 0.7 4.3^((b)) 3.23.1 C12 0.8 — 0.2 0.9 C8 Isomer Relative Distribution [%]Trimethylpentanes 70 81 87 Dimethylhexanes 21 17 9 Octane Number RON 10187 89 95 97 MON 93.8 84 86 92.2 93.4 SIMDIST (ASTM D2887) [° F.] FBP(99.5) 356 376 378 ^((a))C5−. ^((b))C11+.

The results presented in Tables 3 and 5 show that ethylene alkylation atrelatively higher reaction temperatures (e.g., 100° F. and above)provided very high olefin conversion (≥96.0%) and generated alkylatewith high octane numbers (Examples 2 and 3 vs. 4 and 5). This result iscontrary to conventional C4 olefin alkylation, where a relatively lowertemperature (e.g., less than 100° F.) provided 100% conversion and highoctane numbers (Examples 8 and 9). For ethylene alkylation, thedimethylhexane content in C8 isomers significantly increased as thereaction temperature is lowered (Table 3). For C3 and C4 olefinalkylation, lower reaction temperature increases the trimethylpentanessignificantly, the opposite trend (Examples 8 vs. 9). Again, this resultis contrary to conventional C4 olefin alkylation,

Example 10 Composition of Alkylate Gasoline Made by Ethylene Alkylationwith Isobutane

It was discovered that, depending on the process conditions, the C8isomer composition varied significantly. C8 isomers can be predominatelytrimethylpentanes (100-110 RON) or predominately dimethylhexanes (56-76RON). At carefully selected process conditions, C8 isomer compositionwas comprised of over 70% trimethylpentanes.

It was discovered that, at carefully selected process conditions, C6composition was comprised of over 95% 2,3-dimethylbutane (103.5 RON).

It was very surprising to discover that at lower reaction temperature of90° F. and lower reaction pressure of 180 psig, overall C6 selectivitysignificantly decreased and C8 selectivity significantly increased.Also, among C8 isomers, dimethylhexanes significantly increased, andtrimethylpentanes significantly decreased, resulting in poor alkylatequality (lower octanes) clearly indicating that process conditions forethylene alkylation must be carefully selected and controlled.

The study above showed that a new alkylate composition can be obtainedby ethylene alkylation with isobutane with an ionic liquid catalyst atthe preferred process conditions. The composition of the alkylate of thepresent disclosure can be summarized as follows in Table 6.

TABLE 6 Gasoline Alkylate Composition Feature Composition Range CarbonNumber Range  C5-C14 C6 [wt. %] 70-90 C8 [wt. %]  6-30 C9+ [wt. %] <102,3-Dimethylbutane/Total C6 [%] 75-99 Trimethylpentanes/Total C8 [%]50-80

1. An alkylation process comprising: passing an isobutane feed and anethylene feed to an alkylation reactor, wherein the alkylation reactorcontains an ionic liquid catalyst, the ionic liquid comprising anorganic cation and a halometallate anion, for reacting the isobutane andethylene to generate an alkylate having a research octane number (RON)of 93 or more; wherein the alkylation reactor is operated at reactionconditions including a temperature of from 30° C. to 100° C., a pressureof from 300 psig to 700 psig (2068 kPa to 4826 kPa), an overall paraffinto olefin molar ratio from 2 to 20, and a residence time of from 5minutes to 1 hour.
 2. The process of claim 1, wherein the ethylene feedis a dilute ethylene feed stream, a polymer-grade ethylene feed stream,or a combination thereof.
 3. The process of claim 2, wherein the diluteethylene feed stream comprises 5 wt. % to 50 wt. % ethylene.
 4. Theprocess of claim 2, wherein the polymer-grade ethylene feed streamcomprises at least 98 wt. % ethylene.
 5. The process of claim 1, whereinthe organic cation of the ionic liquid comprises an ammonium cation, apyrrolidinium cation, a pyridinium cation, an imidazolium, a phosphoniumcation, or a combination thereof.
 6. The process of claim 1, wherein thehalometallate anion comprises a metal selected from Al, Ga, In, Mn, Fe,Co, Ni, Cu, Zn, or a combination thereof, and a halide selected from F,Cl, Br, I, or a combination thereof.
 7. The process of claim 1, whereinthe halometellate anion is a haloaluminate anion.
 8. The process ofclaim 1, wherein the ionic liquid is present in an amount of from 1 vol.% to 70 vol. % of a total volume of material in the alkylation reactor.9. The process of claim 1, wherein the process has a selectivity for C6of at least 70%, and the alkylate has a mole ratio of dimethylbutane tomethylpentane of greater of at least
 10. 10. The process of claim 1,wherein the alkylation reactor further comprises a co-catalyst.
 11. Theprocess of claim 10, wherein the co-catalyst comprises a Brønsted acidselected from the group consisting of HCl, HBr, HI, and mixturesthereof, or a Brønsted acid precursor.
 12. The process of claim 1,wherein a conversion of the ethylene is at least 95%.
 13. The process ofclaim 1, wherein the alkylate has a RON of 94 or more, or 95 or more, or96 or more, or 97 or more, or 98 or more, or 99 or more, or 100 or more.14. The process of claim 1, wherein the temperature is in a range offrom 35° C. to 70° C.
 15. The process of claim 1, wherein the pressureis in a range of from 350 psig to 500 psig (2413 kPa to 3447 kPa). 16.The alkylation process of claim 1 further comprising: separating thealkylate and unreacted isobutane feed from the ionic liquid to form ahydrocarbon stream comprising the alkylate and the unreacted isobutanefeed and an ionic liquid stream comprising the ionic liquid; separatingthe hydrocarbon stream into an alkylate stream and an unreactedisobutane stream; and recycling at least one of the unreacted isobutanestream and the ionic liquid stream.
 17. The process of claim 16, furthercomprising: regenerating at least a portion of the ionic liquid in theionic liquid stream; and recycling the regenerated ionic liquid catalystto the alkylation reactor.
 18. An alkylate having a research octanenumber (RON) of 93 or more, comprising: (i) at least 70 wt. % C6paraffins, wherein the C6 paraffins comprise isomers of dimethylbutane(DMB) and methylpentane (MP) and a molar ratio of DMB to MP is at least7:1; (ii) 30 wt. % or less C8 paraffins; and (iii) less than 20 wt. %C9+ paraffins.
 19. The alkylate of claim 18, having a RON of at least 94or more, or 95 or more, or 96 or more, or 97 or more, or 98 or more, or99 or more, or 100 or more.
 20. The alkylate of claim 18, comprising atleast 80 wt. % C6 paraffins.
 21. The alkylate of claim 18, comprising 5wt. % to 15 wt. % C8 paraffins.
 22. The alkylate of claim 18, comprisingless than 10 wt. % C9+ paraffins.